1. Field of the Invention
The invention relates generally to threaded fasteners and more particularly to screws having improved locking features for modular framework.
2. Description of Related Art
Many conventional frames, cabinets, tables, partitions and other similar items are made of modular components such as square tubular members which are interconnected by sliding them over projecting arms of a corner connector. Screws inserted into the arms are turned into engagement with the interior wall of the tubular members to secure the corner connector and tubular members together. Modular type assemblies of the above-described nature are widely used in the consumer industry for everything from patio furniture to garage cabinets because the components parts can be readily packaged and the end user can provide the assembly.
Typical examples of conventional modular structures are illustrated in U.S. Pat. Nos. 3,858,989 and 3,854,831. In U.S. Pat. No. 3,858,989, a modular corner joint is disclosed which includes tubular members and a hub corner connector with protruding arms. Conical set screws are inserted into threaded holes which extend laterally through the arms. Once assembled the set screws are backed into a hole in the tubular member such that the screw engages the inner surface of the hole and ultimately locks the tubular member against the corner hub. In U.S. Pat. No. 3,854,831, a corner fitting has projecting arms. Before assembly bolts are inserted into threaded holes in the arms. The tubular members are slid over the arms, and the bolts are backed into the inner wall of the tubular members via an access hole in the wall of the tubular member. Each bolt has a head portion which extends into the access hole and pushes against the inner wall of the access hole, thereby urging the tubular member and the arm into clinching engagement.
While the above described threaded fasteners have meet with a certain amount of success, the interconnected joint arrangements disclosed in these patents are still susceptible to loosening due to vibration or shock because the fastening screws do not provide sufficient surface resistance. Furthermore, in many applications modular joints are not used for fabricating cabinets, frames, tables or partitions because conventional modular structures are not sufficiently stiff or stable. Instead, welded structures are preferred which offer stability, but disadvantageously are very labor intensive to fabricate and therefore expensive.
Therefore, it would be an advancement to the art to provide a simple, inexpensive means to fasten modular components together in stable relationship.